Reciprocating pumps conventionally comprise a “power end assembly” and a “fluid end assembly”. In the power end assembly, rotational movement of a driveshaft drives reciprocating movement of a plunger. In the fluid end assembly, a fluid end body defines a plunger bore in fluid communication with a suction manifold via a suction valve, and in fluid communication with a discharge manifold via a discharge valve. Movement of the plunger in one direction within the plunger bore decreases the pressure of a working fluid in the plunger bore, thus closing the discharge valve and opening the suction valve to allow additional working fluid to flow from the suction manifold into the plunger bore. Movement of the plunger in the opposite direction within the plunger bore pressurizes the working fluid in the plunger bore, thus closing the suction valve and opening the discharge valve to allow working fluid in the plunger bore to flow into the discharge manifold. The foregoing suction and discharge cycles repeat as the plunger moves in alternating directions within the plunger bore.
Erosion, mechanical stress and fatigue of fluid end bodies are acute problems when reciprocating pumps are used to pump abrasive fracturing fluids at ultra-high pressures for hydraulic fracturing operations. Cracking of internal bores and valve seat decks and corrosion of the internal bores of the fluid end body have been observed in practice. Regions of the fluid end body in the vicinity of the valves are particularly susceptible to erosion. These phenomena may lead to failure, reduced performance, and shortened service life of fluid end bodies.
Conventional fluid end bodies have an internal cross-bore configuration with the suction valve and discharge valve received in coaxial, vertically oriented bores for vertical flow of the working fluid from the suction valve upwards towards the discharge valve, and the plunger bore being horizontally oriented for horizontal movement of the reciprocating plunger. This cross-bore configuration results in acceleration of the working fluid from a horizontal direction to a vertical direction as it is pressurized from the plunger bore to the discharge valve and results in geometric discontinuities internal to the fluid end body, which can exacerbate erosion and undesirable mechanical stresses in the fluid end body.
Conventional fluid end bodies have complex contoured and tapered internal bores to receive and retain the valves. Valve seat members made of materials such as hardened steel are forcibly inserted into the internal bores, so that the valve seat members are compressed and wedged into the internal bores, and retained therein by fiction fit. This creates internal mechanical stresses in the valve seat members and the fluid end body, which may be further concentrated by the geometric discontinuities of the contoured and tapered internal bores. The manifolds are then attached to the fluid end bodies. The manifolds must be removed to extract the valves from the internal bores.
Conventional fluid end bodies comprise a single monolithic block defining multiple plunger bores to accommodate multiple plungers. Accordingly, even if damage to the fluid end body is localized at one of the plunger bores, the entire fluid end body must be removed from the power end assembly to service the fluid end body. Further, if the localized damage cannot be repaired, the entire fluid end body must be replaced.
There remains a need in the art for a fluid end assembly that is resistant to wear and failure, and is convenient and economical to service.